Endovascular Treatment The Role of Dominant Caliber M2 Segment Occlusion in Ischemic Stroke

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Publication

Background and Purpose—It is unclear whether endovascular treatment (EVT) is beneficial for patients with acute
ischemic stroke with occlusion of the M2 segment of the middle cerebral artery. We aimed to compare functional
outcomes, technical aspects, and complications of EVT between patients with acute ischemic stroke because of M2 and
M1 occlusions in clinical practice. Furthermore, outcome and complications after EVT in dominant and nondominant
caliber M2 division occlusions were studied.
Methods—Data were obtained from the MR CLEAN Registry (Multicenter Randomized Clinical Trial of Endovascular
Treatment for Acute Ischemic Stroke in the Netherlands) which is an ongoing observational study in 16 Dutch centers
performing EVT in the Netherlands. Functional outcome was measured with the modified Rankin Scale score at 90
days. Neurological recovery (delta National Institutes of Health Stroke Scale), successful reperfusion rates (extended
Thrombolysis in Cerebral Infarction ≥2B), and safety outcomes were also investigated. Associations between occlusion
location and outcome were analyzed with ordinal logistic regression models, with adjustment for other prognostic factors.
Results—In total, 244 (24%) patients with an M2 and 759 (76%) patients with an M1 occlusion who underwent EVT were
analyzed. Functional outcomes were not significantly different between patients with M2 versus M1 occlusions (adjusted
common odds ratio, 1.24; 95% CI, 0.87–1.73). Occurrence of symptomatic intracerebral hemorrhage was also similar for
M2 and M1 occlusions (6.6% versus 5.9%; P=0.84). Further analysis about dominance of an M2 branch was performed
in 175 (72%) patients. Neurological recovery was comparable (mean delta National Institutes of Health Stroke Scale,
−2±10 for dominant M2, −5±5 for nondominant M2, and −4±9 [P=0.24] for M1 occlusions). Furthermore, the effect of
reperfusion status on functional outcome was comparable between occlusion divisions (common odds ratio, 1.27; 95%
CI, 1.06–1.53 for dominant M2; common odds ratio, 1.32; 95% CI, 0.93–1.87 for nondominant M2; and common odds
ratio, 1.35; 95% CI, 1.24–1.46 for M1 occlusions).
Conclusions—Outcomes and complication rates after EVT were similar in patients with M2 and M1 occlusions. Although
based on observational data and a limited sample size, a similar association of reperfusion status with functional outcome
for all subgroups provides no evidence that patients with either a dominant or a nondominant M2 occlusion should be
routinely excluded from EVT.